The present invention relates generally to wide-area radio communication systems, and in particular, to a method for dynamically associating talkgroup communications with an announcement group in a wide area radio communication system.
Wide area dispatch radio communication systems are known. Commercial exemplars of these systems include the SMARTZONE and OMNILINK systems from Motorola Inc., Schaumburg, Ill. In these systems multiple radio base sites are geographically distributed over a wide area to provide over-the-air communications for subscriber radio units travelling in the area. The multiple radio base sites are trunked to a zone controller that performs call control and mobility management for radios and talkgroups on the system. A zone manager is coupled to the zone controller in the system to configure system parameters, physical device configuration, and radio and talkgroup attributes.
In existing wide area dispatch systems, subscriber units are grouped for intercommunication. Talkgroups are groupings of subscriber units that wish to intercommunicate. For example, the fire department of a municipality uses a talkgroup for communication between all members of the fire department. Similarly the police department uses another talkgroup for communication among the members of the department. Another grouping is an announcement group. The announcement group consists of select talkgroups. For example, an announcement group consisting of both the police department talkgroup and the fire department talkgroup accommodates announcements that may apply to both talkgroups.
Traditionally, the association of talkgroups to announcement groups is programmed in the subscriber unit as well as the zone manager and zone controller. In other words, a subscriber unit knows which talkgroups are affiliated with announcement groups. In this manner a subscriber unit, by reviewing the talkgroup associated with a communication determines whether the subscriber unit should participate in the communication because of affiliation with the talkgroup or the announcement group. Since the subscriber unit knows which talkgroups are associated with an announcement group, the announcement group need not be transmitted as a part of each talkgroup communication. If the subscriber unit is set to listen to an announcement group, then the subscriber unit monitors all talkgroup communications associated with the announcement group using the internally stored association between talkgroups and announcement groups. The zone controller uses the stored association of talkgroups to announcement groups to ensure talkgroup and announcement group communications are directed to the correct radio sites based on the radios registered at those sites. This system assumes a static relationship between talkgroups and announcement groups and to some extent a static assignment of talkgroup identification, that is, the actual digital identification sent in a communication and used by a subscriber unit to determine if the communication is directed to it.
Recent standards proposals for wide-area radio communication systems, such as the Association of Public Safety Communications Officers (APCO) Project 25, propose a dynamic allocation of working group or talkgroup identifications. That is, the actual digital data sent with a communication is assigned to a particular talkgroup, rather than having certain digital data always represent the same talkgroup. Since the talkgroup identifications, which are sent in communications for selective reception by subscriber units, are dynamically determined, it is not feasible to statically store in a subscriber unit a predetermined association of talkgroup identifications to announcement groups. This creates a problem for a system that relies on a subscriber unit to use a stored association of announcement groups to talkgroups for monitoring announcement group communications.
Therefore a need exists for a method for a subscriber unit to dynamically associate communications with an announcement group or talkgroup.